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Old Sep 20, 2002, 07:27 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
At the time the Fokker D-VII was produced during WWI, it was manufactured in Germany, by a number of firms including Fokker. But, it was designed by Fokker, who smuggled a couple train loads of D-VII's and parts out of Germany back to the Netherlands at the end of the war. After WWI the D-VII was produced in Holland by the Fokker company and sold to a number of countries, including the US who used them for trainers. So, *DURING* WWI it would be a stretch to call the D-VII a Dutch plane. It was designed by a Dutch aircraft designer/manufacturer who was operating his business in Germany during WWI. In the competition for the fighter contract that that led to the DVII, Fokker submitted something like 10 different planes and designs. The D-VII was the winning design. There were so many that Fokker numbered them.

This is all off the top of my head, but I thinkit is relatively accurate with regard to the D-VII. I can type in more tonight when I'm home.

Gordon
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Old Sep 24, 2002, 03:55 PM
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I'm a little concerned about weight on my 2X version. I found some wide tip ink markers at a LHS. They claim "non-toxic, water resistant, smear-proof". The test piece I did looked fine, and the ink dried very quickly. So I'm hoping no more than .5 oz on the finish. However, my choices of power systems have me concerned. They are:
  • EDF50 / DXA gearbox / 7x300 NiMH; total = 2.875 oz.
  • Mabuchi 050 / Maxon 4:1 / 8x300NiMH; total = 3.25 oz.
  • EDF50 / DXA / 2xQC830; total = 3.375 oz.
The prop (APC 7x5 thin E) and prop adapter for all three will be the same, and weigh 1 oz. total. Throw in 3.125 oz. for the bare wood parts, and 1.5 oz. for all of the electronics. So I'm looking at a minimum of 8.5 oz., plus LG and wheels. I'd really like to use the EDF50 / QC combo, but that's another .5 oz., and the wing area is only 133 in^2. I'm planning to trim the wires on the servos and ESC, and solder the connections directly to the R4P, so that should cut about .5 oz. I know the EDF50/QC combo can easily lift 8.5 oz, but it's the wing loading that has me concerned. I figure the best I'll probably do is about 9 oz./ft^2. Think that's OK for one of these little guys?

Tony Turley
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Old Sep 24, 2002, 04:12 PM
Just an average RC'er
Jim McPherson's Avatar
Laurel, Maryland USA
Joined Aug 2000
4,291 Posts
3.125 Oz for the bare wood sounds REALLY high. Considering that a heavy regular version weighs 15 grams. In addition you'll never lose 14 grams (0.5oz) from trimming the RX, servo and speed control wires. Think about it: Servos:nothing fancy say 6 grams each x2 = 12 grams. RX GWS R4P = 5 grams, speed control = 2 grams. Total of 19 grams. You won't be shaving all of that down to 5 grams. Using LI-Poly cells will get your weight down a bit, but with wood that seems to be as heavy as oak, you'll not get far. It will probably fly, but REALLY fast.
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Old Sep 25, 2002, 12:11 AM
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Chris3D's Avatar
New Paltz, NY, USA
Joined Apr 2001
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Hi Tony, I have to agree with Jim, 3 and 1/8 ounces for the bare wood seems awfully heavy. Using contest grade wood, the parts for a 12 inch version (stained and everything) weighs about 8 grams. I'm honestly not sure how to suggest you proceed. Was the wood you used overly dense? You could try building a new fuselage out of light 1/32 inch wood - with the closed construction, it'll be plenty strong. If you're using markers, you shouldn't gain 1/2 an ounce, but I'd definitely recommend you color in the stripes and leave the rest of the wood bare just to be on the safe side.

Can you get away with a single QC cell (I've never used them, so I have no idea...), or even some of the 230mah LiPolys?

Mine has about 36 sq. inches of wing area, which is a 1/4 foot. At not over an ounce (it's actually a few grams under, or was before several crashes and some additional glue), that puts it at 4 oz. sq. foot wing loading. It flies really well, and I'm sure it'd fly fine even heavier, but more than doubling the wing loading is a bit scary. I would try to get it somewhere in the 6 to 7 oz range if at all possible.
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Old Sep 25, 2002, 09:14 AM
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I must have had a brain flatulation when I wrote 3.125 for the bare wood parts. I went back and weighed them again, and they were 2 3/8 oz. Still not super light, but I don't know where I picked up the extra 3/4 oz. I had a bunch of figures written down on the front of the instruction booklet, so I probably just made a math error.

More good news: I decided I didn't have anything to lose, so I went ahead and "painted" the fuselage with the ink marker - and the after-finish weigh-in showed no weight gain! Granted, my scales only have a resolution of 1g, but I feel pretty good about only adding <1g to the fuselage for the red color! I'm going to proceed with coloring the rest of the parts. Here's a photo of the markers I'm using, $1.99 each at a LHS. The ink penetrates the wood evenly, too, without the streaking effect common with many magic markers.

Tony Turley

EDIT: If I remember my math correctly, by doubling the size of the model, the volume of wood I'm using increases by a factor of 4 - if I was using the same thickness of wood. But since I went from 1/32" to 1/16", then I'm essentially using 8x as much wood! IF my wood density was the same as the original, then I'd be looking at approximately 64g worth of wood. However, I didn't use contest grade; I just picked the best pieces of Bud Nosen balsa I could find at the LHS. 2 3/8 oz is about 67g, so let's say about 70g finished weight for the wood. In retrospect, that doesn't sound too bad.

EDIT #2: I need to start getting more sleep. The 1.5 oz I quoted above for the electronics sounded fishy, so I weighed them again. The correct figure is 0.5 oz. I stuck a fresh battery in the scales and reweighed everything to make sure. It looks like my flying weight will be 7.5 oz., which yields 8.1 oz./ft^2. I can live with that. Furthermore, after coloring the entire plane with the ink markers, the scales are still indicating <1g of weight increase vs. the bare components. Life is good!
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Last edited by t-turley; Sep 27, 2002 at 04:18 AM.
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Old Oct 11, 2002, 08:15 PM
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Jeff Meyers's Avatar
Fayetteville, GA
Joined Oct 2000
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Can someone provide a link to the software to view the video?
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Old Oct 11, 2002, 08:22 PM
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dhurd's Avatar
Buffalo, New York
Joined Jan 2002
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www.divx.com.
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Old Oct 14, 2002, 11:01 AM
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San Mateo, CA
Joined Mar 2002
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li-poly connection in the pitts

I've almost finished my micro pitts and have one last problem - wiring in the battery!

What type of plug and socket do you use between the li-poly battery and wires leading to the receiver? My first attempt with a magnet coupler (from the didel web site, using two 1/16*1/32 magnets) just didn't seem reliable enough, and the lightest sockets I can get are 0.3grams which seem way to heavy.

Any advice would be most appreciated!

Martin
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Old Oct 14, 2002, 02:07 PM
Team 30 Micro EDF
Mike Taylor's Avatar
Camarillo, California
Joined Apr 2002
4,516 Posts
I usually solder leads to the batteries. Then, for planes with built in systems, I solder the leads into the charging jack / switch assembly, and plug the leads from the switch into the receiver. On planes where I want to change batteries, I just mount the battery with velcro, and plug the leads directly into the receiver (and use an alligator-clip adapter for the charger to charge the loose batteries).
I am intriqued with the idea of using magnets to hold the foil tabs (battery terminals) to steel contacts, but I think you would need velcro to hold the battery in place to keep from tearing off the foil tabs in a crash. This method makes it harder to adjust the CG by moving the battery around, though. But turning the unit 'off' would just require removing a magnet...
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Old Oct 14, 2002, 10:49 PM
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Albuquerque, NM
Joined Oct 2002
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would it add too much weight to airbrush this plane lightley?
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Old Oct 15, 2002, 04:43 PM
www.toddsmodels.com
Todd Long's Avatar
North Bend, WA.
Joined Apr 2000
1,832 Posts
I just found a website with movies of a Micro Pitts flying.

http://www.geodesicjapan.com/YSFC/Ev.../Flight23.html



Todd
www.toddsmodels.com
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Old Oct 15, 2002, 07:51 PM
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dhurd's Avatar
Buffalo, New York
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Yikes!!! Looks like he was a little bit tail heavy. Unless I missed a movie.
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Old Oct 17, 2002, 10:27 PM
Registered User
Gladstone, NJ. USA
Joined May 2000
408 Posts
Hi Guys!
Great plane and great plans...I have a question that someone brought up earlier..which is...What method or piece of software did you use for developing the flat pieces from the "rolled model"
I'd real like to know in detail..
Sincerely,
Jon B. Shereshaw
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Old Oct 19, 2002, 03:29 PM
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Leicester England
Joined Jun 2001
591 Posts
Patterns for fuselages

To be able to produce the pattern you have to do a five year apprenticeship in engineering sheet metal work.
After that, your job goes to China!
But what the hell, plenty of time to make patterns for fuselarges!

I cant spel because I was learning enginering which is done with drawings not words.

I did a little article about making the patterns for WAYNES INDOOR WORLD (remember that?) also between me and Wayne we lost half of it, maybe its still going round and round the internet?

Anyway, I have kept all the patterns of the planes I have ever made and you coudl learn to if you made foam planes starting with square simple fuselages like Jigglets and moving on to round planes like Tangos, after that we have P51's, F86's B25's Lancasters, Corsairs and Albatrosesess

I am sure there is a computer pattern generators somewhere but it will be commercial stuff and cost a lot of money.

Mark
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Old Oct 20, 2002, 02:00 AM
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Chris3D's Avatar
New Paltz, NY, USA
Joined Apr 2001
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Thanks for the link, Todd, it's interesting to see the plane being built by others around the world. As best as I can make from a web translation of the page, unfortunately they were not terribly successful. Looking at the videos, it's clear the plane was way too tail heavy, and at 35 grams, it's over 20% heavier than mine overall. Also, looking at the top-view photo, it doesn't appear the motor was set with ANY right thrust, let alone the 6 degrees the plans clearly states is necessary. When you're only dealing with a few dozen sq. inches of wing area, you just can't disregard weight. I'm sure the full paint, as opposed to stain and paint, and the 230mah LiPoly are the main culprits, but I would think it'd still fly with the correct CG. Mine flew quite easily tonight on 1/3 to 1/2 throttle, as David and Gordon can attest to, and David had no trouble flying it himself (I wish I could say the same of my flights with his Wisp ).

JonB, I started by taking a 3-view image of a Pitts and tracing the overall side-view of the fuselage in an illustration program (I use Freehand, but you could use any other vector based drawing program, or even tracing paper and a pencil). I extended the fuselage quite a bit for the turtle deck, the area in front of the cockpit, and the lower cowl. I then printed and cut the pieces out of paper and test fit them over balsa fuselage formers, trimming the paper where necessary. Once the paper pieces were fitting well, I updated the outlines to reflect the modifications made to the paper pieces. At that point, I built an entire plane out of balsa (the original, bare wood, Pitts), making minor changes to the outlines as necessary - usually just enlarging things very slightly to compensate for the thickness of the wood, as opposed to paper. At that point, the plans were fairly refined, and I built the current red version.
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Last edited by Chris3D; Oct 20, 2002 at 02:05 AM.
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